1. Field of the Invention
The present invention relates to a stereoscopic display, and more particularly, to a time-sequential stereoscopic display.
2. Description of Prior Art
Human beings see real-world images using both eyes. Further, the human brain forms three-dimensional (3D) images according to differences in spatial distance between two views seen by both eyes from two different angles. A 3D display is designed to create simulations of human visual fields from different angles to help users perceive 3D images when viewing two-dimensional (2D) images.
Currently, 3D displays are divided into two categories. One is auto-stereoscopic displays; the other is stereoscopic displays. Users of auto-stereoscopic displays are able to view 3D images without wearing glasses with a unique structure while ones of stereoscopic displays have to wear specially designed glasses to view 3D images.
The principle of a 3D display of parallax barrier patterns inside auto-stereoscopic displays is that, based on an opaque parallax barrier, users of auto-stereoscopic displays are able to view parallax images with both eyes, and such a parallax produces the third dimension in the brain. The principle of a spatial sequential 3D display is that a time-irrelevant parallax barrier is employed to let both eyes see two different groups of pixels, and the two groups of pixels are provided with signals from the left and right eyes, respectively, so both eyes can view different images. But, the drawback is that the resolution declines to one-half of the original resolution. The principle of a time sequential 3D display is that a time-manipulating and synchronously-driven-with-display-panel parallax barrier is employed to let both eyes see the same group of pixels at different time points. This group of pixels is supplied with signals of left and right eyes at different time points, respectively, to let each eye view different images. However, considering that a single human eye must receive signals of 60 Hz to avoid perceiving flicker, a time sequential 3D display usually requires a frame rate of at least 120 Hz.
Referring to FIG. 1 showing a schematic diagram of a time sequential 3D display device 10, the display device 10 comprises a liquid crystal panel 12 and a barrier 14. The liquid crystal panel 12 comprises a pixel matrix. The barrier 14 has multiple stripe openings 14 (a) thereon. With the use of the above-mentioned barrier 14, left-eye and right-eye images are separated, and then the separated images are reflected into a viewer's left eye L and right eye R, respectively. At frame N, pixels of odd columns are displayed based on left-eye signals, while pixels of even columns are displayed based on right-eye signals, and the barrier 14 is deemed to operate in “LR mode”. While at frame N+1, pixels of odd columns are displayed based on right-eye signals, while pixels of even columns are displayed based on left-eye signals, and the barrier 14 is deemed to operate in “RL mode”. Because the liquid crystal panel 12 adopts a row-by-row scanning, column numbers distributed by left- and right-eye signals on the upper part of the liquid crystal panel 12 are different from those distributed on the lower part when the frame of the liquid crystal panel 12 is updated medially. Take FIG. 1 for example, signals received by pixels on the upper part of the liquid crystal panel 12 are in RL mode while signals received by pixels on the lower part are in LR mode. However, if the barrier 14 as a disparity barrier is in motion at the same time, the human eye will receive mixed left- and right-eye signals in the end.
There are two approaches to avoid the above-mentioned problem: one is black frame insertion (BFI) and the other is dynamically switching the backlight module. The BFI approach proceeds as follows: After a frame where images are displayed according to odd columns with right-eye signals and even columns with left-eye signals is shown, insert a black frame and then another frame where images are displayed according to odd columns with left-eye signals and even columns with right-eye signals. Repetitively, insert a black frame and then another frame where images are displayed according to odd columns with right-eye signals and even columns with left-eye signals. As for dynamically switching the backlight module, the method is as follows: when a liquid crystal panel is scanning, the backlight module is turned off. Then the frame will hold its state for a while after finished being scanned, the backlight module will be turned on at this time. Then the liquid crystal panel will continue scanning the next frame, and the backlight module is turned off again. Unfortunately, the two approaches share a common problem; that is, a refresh rate higher than 120 Hz is required (e.g., 240 Hz is needed for the BFI method) in order to permit the human eye receive frames at 60 Hz. This will produce additional power consumption and increase design complexity.